1. In homeopathy, a block to healing or a general weakness caused by a predisposition to a particular disease in someone or in his or her family that is transmitted down the generational chain.
2. Unhealthy vapors rising from the ground or other sources: Certain lakes are usually full of vegetable matter undergoing decomposition and they often produce large quantities of miasms.

This miasm unit is usually a spelling variation of "miasma".